In researching it, oversizing the scrubber would simply give you a quicker "scrubbing" ability...meaning it would be able to handle a higher bi-load and also remove spikes more quickly. You can go 2 different routes, pump fed or overflow fed. I personally went with overflow fed for the simple fact hat I didn't see it efficient to have to run yet another pump when I had decent existing flow. All in all, you could make it any size you want, as long as you maintain the 35gph.. which the reason for that number is because water rushing over algae at that rate actually causes the molecular filtering of the water. Something that's not accomplished outside of that. I wouldn't go any higher than 35 gph
, once you see the flow in person, you'll understand. Its a pretty high flowrste for such a relatively small area. Oh and lighting is a BIG factor...gotta light both sides and as evenly as possible. I believe its roughly 2-3 watts per square inch.